Cosmetic and reconstructive implants are widely used in cosmetic and reconstructive corrections. One of the commonly use substances as the implant filling material is silicone gel. It has been used for various facial implants, such as brow, nose, cheek, chin and lips, and various body implants, such as pectoral and breast, triceps and biceps, genitals, buttocks and calf. Among all types of cosmetic and reconstructive implants, the breast implant is the most prevalent and, hence is addressed with specific emphasis hereinafter.
Over the last four decades, surgical breast augmentation in the United States has been primarily achieved through placement of breast implants. Implants are surgically placed either in front of the pectoralis major muscle, called subglandular or prepectoral implants, or they are placed behind the pectoralis major muscle, called submuscular, retroglandular, retropectoral, or subpectrol implants. The type of the material in the implants and the variations in the shape and supporting shells of the implant may also vary. A silicone gel-filled implant is generally composed of silicone gel contained within a silicone polymer membrane or envelope. A saline implant is generally composed of saline contained within a silicone polymer membrane. A double-lumen implant generally refers to an implant having two shells, typically an inner shell filled with silicone gel surrounded by an outer shell filled with saline. A reverse double-lumen implant generally refers to an inner shell of saline surrounded by silicone. Other variations have been implanted with three or more shells.
Before 1992, the majority of breast augmentation implants in the United States contained silicone gel. This was due to general acceptance by the medical community at the time, surgeons' preference, and the reported better texture and “feel” of a silicone gel-filled implant versus a saline-filled implant by the patients. It has been estimated that over one million women in the United States alone have received silicone gel-filled breast implants. In the 1980s, independent authors questioned a possible association between silicone gel-filled implants and the subsequent development of connective-tissue diseases. Fueled by media hype and class action lawsuits, the Food and Drug Administration (FDA) was asked to analyze the data and make a decision. In 1992, the FDA announced that breast implants containing silicone gel would only be available in the United States under clinically controlled trials. It has since been primarily restricted in the United States to women undergoing post-mastectomy reconstruction and those requiring secondary surgery after breast augmentation. Saline-filled breast implants have replaced silicone gel-filled implants as the common breast prosthesis in the past decade. However, in comparison to silicone gel-filled implants, saline-filled breast implants are inferior in terms of mimicking elasticity, feel, and movement of the natural breast tissue. Since 1992, there are many studies investigating the safety concerns of the silicone gel-filled implants. In 1999, after reviewing dozens of studies, the Institute of Medicine (IOM) concluded in its landmark 1999 report that silicone gel-filled implants do not cause the autoimmune disorders such as lupus or arthritis. The main safety concern according to the report is the implants' tendency to rupture. The silicone can bleed or leak out of its shell, causing infections, and/or local tissue reactions. The IOM 1999 report became the turning point for the breast implant industry and the plastic surgery profession, opening the door for the return of silicone gel-filled breast implants for cosmetic use.
Silicone gel-filled implant rupture is often locally symptomatic, and continues to be a genuine clinical concern for patients and physicians. In the United States, an estimated one to two million patients, or approximately 1% of the adult female population, have breast implants. Generally, the risk of implant rupture increases with the age of the implant. One recent study revealed that the median lifespan of a silicone gel-filled breast implant is 16.4 years. In that study, 79.1% of implants were intact at 10 years; the percentage decreased to 48.7% at 15 years. Another study revealed that at least 77% of 344 women from Birmingham, Ala. who were not referred for examination had at least one implant that had “ruptured” or had an “indeterminate” finding upon MRI. The reported median implant age at rupture was 10.8 years, and submuscular implants were more likely than subglandular implants to rupture.
In essentially all patients, a fibrous capsule forms around the implant i.e., encapsulation. The capsule may be soft and nonpalpable or hard and resistant. Generally after implantation, two types of silicone gel-filled breast implant ruptures can occur: intracapsular rupture occurs when silicone escapes the elastic membrane shell but is contained in the fibrous capsule. This form of silicone gel-filled breast implant rupture is most common. Extracapsular rupture involves the escape of free silicone gel through the fibrous capsule, with extravasation into the breast tissue. Migration of silicone gel to the axillary lymph nodes also may be present. Furthermore, silicone gel can migrate to the brachial plexus, chest wall, axilla and the wrist.
In attempts of reducing the likelihood of implant rupture, improvements have been made to the structure of the implant envelope or shell. U.S. Pat. Nos. 4,455,691 and 4,472,226 disclose a three layer implant wall comprising a middle layer made of a heteropolymer of dimethylpolysiloxane and siloxane elastomer, which substantially impedes the migration of silicone gel. Commercially, breast implants constructed with low diffusion silicone elastomer shells are available from the INAMED Corporation, Santa Barbara, Calif. The low diffusion shell has a barrier coat between two layers of silicone elastomer to minimize silicone diffusion. U.S. Pat. No. 5,630,844 discloses another three layer implant shell which comprises a hydrophobic thermoplastic elastomer middle layer as a water vapor barrier, which can be used with a broader scope of filling materials and can reduce ruptures due to fold flaw fracture caused by loss of water vapor from the shell.
Furthermore, a new cohesive silicone gel has been developed and is already in use for breast implants in Canada, Europe and other countries. The cohesive silicone gel is expected to be approved for breast implants in the United States in the near future. Different from the silicone gel traditionally used for breast implants, cohesive silicone gel does not leak out from the shell of the implant. However, when the implant shell ruptures, the patient's tissue will be in contact with the cohesive silicone gel, which can potentially cause inflammation and other mal-effects of silicone to the human body.
The diagnosis of silicone gel-filled breast implant rupture is critically useful to both clinicians and patients. It aids in surgical decision-making and helps the patient gain peace of mind. Furthermore, it avoids the risk of any illness to patient, including any potential systemic effects of leaked silicone gel-filled breast implants, if any, which presently remain unclear. Currently, magnetic resonance imaging (MRI) is used to evaluate silicone gel-filled breast implants, because the findings at clinical examination often are nonspecific. However, MRI is an expensive examination involving complex instrumentation and data processing. Having regular-scheduled MRI's to detect a rupture, preferably sooner than later, is impracticable due to the expense, the complicated nature of the procedure, requirement of multiple parties including medical personnel, and inconvenience to patient.
As of this writing, the current state of the art as recommended by the FDA (Food and Drug Administration) for women with gel-filled implants is, that should a women and/or her physician suspect a rupture of an implant, the patient is to be referred for immediate Magnetic Resonance Imaging (MRI) utilizing a breast coil to either rule out or confirm a compromise of the implant. However, what is troubling about this is, when gel-filled implants rupture, they rarely cause pain or other immediate symptoms, therefore the women doesn't know to seek medical care. It has also been recommended that MRI'S, which are extremely costly, be performed every two years as a screening technique. What of the period of time between screening MRI's when even the smallest rupture of the envelope can result in the silicone gel being in contact for a prolonged period with the patient's tissues?
Thus, there remains a need for improved detection methods available to the patient herself to detect a possible rupture or impending rupture, and be warned or signaled that she needs to seek medical attention. Further, there remains a need for improved implants that prevent leakage of implant filling material and also incorporate technology and warning mechanisms such that the implant warns or signals a patient of rupture or impending rupture and leakage, preferably prior to leakage of implant filling material.